1. Field of the Invention
This invention relates to a process for producing a denitration catalyst. Particularly, it relates to a process for producing a denitration catalyst for ammonia reduction, using an inorganic fiber cloth as its base material.
2. Description of the Related Art
Denitration catalysts for exhaust gases using as the base materials thereof, the inorganic fiber sheet such as inorganic fiber woven fabric, mat, making sheet, etc. have so far been known, and many inventions have been made. As representatives of such catalysts, a catalyst obtained by supporting a catalyst composition on a silica fiber woven fabric (Japanese patent application laid-open No. Sho 52-37592), a catalyst obtained by dispersing ceramic fibers and a catalyst composition powder in water, followed by making the dispersion into a sheet form according to making process (Japanese patent application laid-open No. Sho 55-39256), a catalyst obtained by supporting by impregnation, a catalyst component on a honeycomb-form carrier prepared by adhering ceramics sheets in a corrugated form (Japanese patent application laid-open No. Sho 59-193139), etc. have been known.
In general, in denitration apparatuses for exhaust gases such as boilers, it is necessary to use a catalyst in a quantity of several tens to several hundreds m.sup.3 per one plant. Thus, as such a catalyst, a product having a large structural body and a high strength are required. Further, exhaust gases often contain corrosive gases including sulfur oxides besides a large quantity of dusts. Thus, it is necessary for the catalyst to retain its activity and strength for a long time even in such corrosive circumstance.
While the catalysts disclosed in the above prior art have many advantages of being light, difficult to be cracked by impact, etc., the above-mentioned requirements have not been met sufficiently and when the catalysts have been made up into a structural body of catalyst, they have been inferior in the aspect of strength and economy to a catalyst using a metal substrate or a honeycomb catalyst prepared according to extrusion-molding process; thus they have not always often been employed.
As described above, in the prior art, a sufficient consideration in the aspect of strength and production cost has not been taken; thus a problem has been raised for obtaining a large-size catalyst in a large quantity.